Girls Learn The Maths Behind Catching Criminals

Dr Terrence Etchells visited the school to give a talk on how maths is used to catch criminals. As a researcher in the Department of Mathematics and Statistics at Liverpool John Moores University, he specialises in the kind of work which the police find particularly useful.

He opened the talk by reminding the girls that mobile phones and social networks have changed the way that police gather intelligence about suspects. He explained that data can be extracted from smartphone, and using mathematics, algorithms and fast computers, links between criminals can be found. It would not be possible for a human being to make these connections by just looking at the data.

Dr Etchells used an example from his own work to illustrate the point. He asked the police if he could have access to the phones belonging to sixty-four different criminals who had been convicted in one area, all of them from seemingly different court cases. He then showed the girls a visualisation of all the different connections made by these phones – which was indecipherable due to the sheer size. There were hundreds, perhaps even thousands of connections, interconnections and networks, even from just those sixty-four phones. However, using a computer programme to put together an adjacency matrix and a visualisation for this, he was able to find communities.

Maths and computer software working together revealed the underlying structure to the raw data – and a common connection between all the different networks. This person, who has connections to sixty-four separate convicted criminals, is likely to be of interest to the police.

The talk was a fascinating look both into the world of mathematics beyond the classroom, and into modern policing.

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Dr Terrence Etchells with two girls who attended the talk

Dr Etchells showed the girls an example of the type of adjacency matrix used in his work